Reliable navigation systems have always been essential for estimating position during flight. For example, traditional altimeter measurements determine the altitude of an aircraft above a fixed level by measuring air pressure (where air pressure decreases with an increase of altitude). A radar altimeter measures altitude by using the time for a radio signal to reflect from a surface (terrain) back to the aircraft. For example, the radar altimeter measures exact height during landing and when the aircraft (in particular, a rotary-wing aircraft) is in a hover mode. Radar altimeters are typically included as a component in various on-board avionics systems. In each on-board avionics system, the radar altimeter component informs an operator (pilot) that the aircraft is flying too low or that terrain is rising to meet the aircraft.
Traditionally, accepting a certain level of altimeter sensor noise is accommodated for when measuring altitude in conditions similar to those described above. As the complexity of aircraft operations (missions) increase, reducing this noise (jitter) becomes significant for ensuring a high level of measurement reliability. Traditional filtering methods that stabilize altitude measurements mainly rely on post-processed data. This post-processed data may not be responsive to rapid changes or random variations in the aircraft's altitude. Additionally, current filtering methods are generally not reflective of terrain conditions, mission status, and other operating modes where minimal noise levels are essential for proper altitude measurement processing.